# Resistance and Inductance Measurement of DC Brushed Motor without rotating

#### vuvuzela

Joined Sep 24, 2018
1
Hello

I'm working on a project which includes Current Control of a DC Brushed Motor. For design a good PI controller, I need to identify the resistance and inductance of the motor. I should not rotate the motor because motor system is already on a system. I might use impulse signal such that system rotates a little while and then stalls. I cannot lock the rotor for testing since motor is in a closed system. I might use sinusoidal signals(I tought for measuring of inductance).
I'm very thankful for the all answers.

Vuvuzela

#### John Caldwell

Joined Sep 25, 2018
3
Hello

I'm working on a project which includes Current Control of a DC Brushed Motor. For design a good PI controller, I need to identify the resistance and inductance of the motor. I should not rotate the motor because motor system is already on a system. I might use impulse signal such that system rotates a little while and then stalls. I cannot lock the rotor for testing since motor is in a closed system. I might use sinusoidal signals(I tought for measuring of inductance).
I'm very thankful for the all answers.

Vuvuzela
Hi There Vuvu. Place a known value capacitor (not electrolitic) in parallel with the motor. Connect a sin wave signal generator to the motor. Place an oscilloscope across the motor. Vary the frequency to find the resonant frequency. You will know that you have hit the resonant frequency when the voltage on the scope jumps up. You may have to experiment with the size of the capacitor to get a resonant frequency in the range of your signal generator. Calculate the value of L using the equations found here: https://www.electronics-tutorials.ws/accircuits/parallel-resonance.html

#### Sensacell

Joined Jun 19, 2012
3,140
Connect it to an LCR meter?

You might need to twiddle the rotor a bit to get the brushes to make clean enough contact for a good reading